1. Field of the Invention
The present invention relates to a defective power source detection method and apparatus for a power source supply system structured by including a plurality of power source apparatus to supply the power source voltage to an apparatus requiring the large power such as a semiconductor testing apparatus.
2. Description of the Related Art
By taking a semiconductor testing apparatus as an example of an apparatus requiring a power source with the large power, the structure of a power source supply system for the semiconductor testing apparatus will be shown in FIG. 4. In FIG. 4, the power source supply system has: a power source apparatus 200-1, 200-2, . . . , and 200-N; a defect detecting circuit 210 to detect the defective state of each of power source apparatus 200-1, 200-2, . . . , and 200-N, and to control start/stop of each of power source apparatus corresponding to the detection result; and a control circuit 220 to control the operation of the defect detecting circuit 210.
Numerals 100A and 100B are power source supply lines of the semiconductor testing apparatus, and output ends of each of power source apparatus 200-1, 200-2, . . . , and 200-N are connected to the power source supply lines 100A and 100B, so that the power source voltage is supplied by operating a plurality of power source apparatus 200-1, 200-2, . . . , and 200-N in parallel.
The power source apparatus 200-1 has an inverter 202-1 and a rectifying and smoothing circuit 204-1, and the output ends of the rectifying and smoothing circuit 204-1, that is, the output ends of the power source apparatus 200-1 are connected to the power source supply lines 100A and 100B. Further, the output voltage of the rectifying and smoothing circuit 204-1 is monitored by an output voltage monitoring circuit 206-1 which is housed in the power source apparatus 200-1. The structure of each of power source apparatus 200-2 to 200N is the same as that of the power source apparatus 200-1.
The defect detecting circuit 210 has a gate 212 to fetch the monitoring voltage (the output voltage of the rectifying and smoothing circuit) of the output voltage monitoring circuits 206-1 to 206-N, which are housed in the power source apparatus 200-2 to 200-N, a latch circuit 214 to hold the output of the gate 212, an OR gate 215, a gate 216 to fetch the output of the latch circuit 214 in the control circuit 220, and the power source start/stop circuit 218.
In the above structure, the output voltage monitoring circuits 206-1 to 206-N of the power source apparatus 200-1, 200-2, . . . , and 200-N, monitor the same voltage in the power source supply lines 100A and 100B. In this state, when a defect is generated in the specified power source apparatus, for example, the power source apparatus 200-1, the voltage level in the power source supply lines 100A and 100B is changed. Each of the output voltage monitoring circuits 206-1 to 206-N compares the reference voltage being provided therein with monitoring voltage in the power source supply lines 100A and 100B, and according to the result of the comparison, outputs a defect detecting signal. Because the output voltage monitoring circuits 206-1 to 206-N monitor the same voltage in the power source supply lines 100A and 100B, the defect detecting signal is outputted from each of output voltage monitoring circuits 206-1 to 206-N to the defect detection circuit 210, and is held in the latch circuit 214 through the gate 212.
The timing of the latching of the defect detecting signal in the latch circuit 214, is the timing at which the first defect detecting signal of a plurality of defect detecting signals outputted from the output voltage monitoring circuits 206-1 to 206-N, is inputted into the latch circuit 214. Incidentally, a plurality of defect detecting signals outputted from the output voltage monitoring circuits 206-1 to 206-N are not necessarily defect detecting signals outputted from the defective power source apparatus because the difference of time is generated in the input timing in the latch circuit 214 due to fluctuations of the characteristics of the elements constituting each output voltage monitoring circuit.
Further, the control circuit 220 generates a reading signal to confirm the existence or not of the defect detecting signal, periodically, and when the defect detecting signal is confirmed, outputs a power source stop command to the power source start/stop circuit 218 in the defect detection circuit 210. The defect detection circuit 210 outputs a power source stop signal to stop the power source supply to each power source apparatus 200-1, 200-2, . . . , and 200-N, according to either one of the power source stop signal from the control circuit 220, or an OR output of the defect detecting signal outputted from the OR gate 215. After the power of each of power source apparatus200-1, 200-2, . . . , and 200-N is stopped, the defective power source apparatus (in this example, the power source apparatus 200-1) is replaced.
In the above conventional power source supply system, after the power of each of power source apparatus 200-1, 200-2, . . . , and 200-N is stopped, the defective power source apparatus is replaced, however, because the defect detecting signal held in the latch circuit inverter 214 not necessarily corresponds to the output of the defective power source apparatus, the power source apparatus which is in the defective state, can not be accurately specified. Accordingly, in the worst case, because it is necessary that the power source apparatus is replaced several times, there is a problem that a long period of time is necessary for the replacement operation of the defective power source apparatus.